A few nights ago I heard an awful noise coming from my basement. I ran down there and heard the noise coming from a covered hole (in the cement floor) with pipes leading out of it up into my water pipes. I noticed in my electrical box a switch labeled "ejector pump". Please tell me what this ejector pump does....I have lived in my house for a year and never heard this horrible noise before now. It has come on twice more since a few nights ago. I have a regular sump pump and understand the concept of the sump pump but have no idea what this ejector pump does and why I have not heard it before now. Please let me know so I won't worry that my basement will explode.